OEM Switch Backlight Integration

HOW TO GET YOUR TOYOTA OEM INTEGRATING BACKLIT SWITCHES TO COME ON AND DIM

So I recently added some lights to my car, as many 4Runner owners do, and wanted an oem-looking switch with a nice backlight that looks like and matches the OEM dimmability. It seems like Ch4x4 makes almost all of the "OEM" toyota switches out there with whichever "ditch-lights" "sasquatch lights" pattern you want, and many websites like yotaxpedition or cali-raised sell them. I finally saw a reddit post in r/4runner where I posted a reply, and now feel the need to type out a step-by-step explanation of how to do this since I am unable to find a good explanation anywhere here or elsewhere.

There are a couple problems with doing this:

1. Getting the backlights to come on
2. Getting the backlights to dim
3. Getting the brightness to match

Here's how I did it with some photos and more in-depth explanation (reddit post here):

I've done this on my 5th gen and it is a pain in the BUTT to get it to work. Do NOT do this if you don't feel comfortable CUTTING your car's wiring harness and soldering it back together. Make sure to use proper insulation when you do so.

I've used these solder splices for most of my wiring. They're super easy to use with a little butane torch but do some practice runs first:

$5 120PCS Heat Shrink Solder Seal Wire Connectors Kit, Waterproof Butt Connector Heat Shrink Electrical Terminals, Professional Insulated Solderless Wiring Splice Connectors

https://www.amazon.com/dp/B0DNR2RYXF

Below are attached the schematics for the OEM switch (top, momentary on, pinout and wire colors for my 2018 sr5 wiper defroster switch, yours may be different) and the Ch4x4 switch (bottom, push on-push off).




It's important to note that the backlight comes on when pin 3 of the OEM switch is connected to 12v by the car's internal system. Pin 2 of the OEM switch is connected to a PWM ground that controls the duty cycle (percentage of time that the backlight is turned on for) and thus can vary the observed brightness.

In order to make the backlight on the Ch4x4 switch work (and dim) with the OEM lights:

Connect the Ch4x4 switch:

1. Use 12V from a fused source. Most led light-bars come with a harness that includes a fuse for the whole system. do NOT get 12V from the 12v pin 1 (+12v) of the OEM switch, it will fry the existing fuse.
2. Connect the switch output to the high side of your relay coil
   
3. Splice the Switch Backlight wire to the green wire on the OEM switch (pin 3, backlight +)
4. Splice the Gnd wire to the white wire on the OEM switch (pin 2, backlight -)

The splicing part can be kind of nasty, since it requires that you cut, strip, and solder wires to your OEM harness. If anyone finds a better solution please don't hesitate to let me know.

(optional) Make the backlight of the Ch4x4 switch match the brightness of the OEM switches:

1. Carefully disasssemble the Ch4x4 switch, you will need to use a knife or small screwdriver, but don't need to cut anything or break any glue bonds
2. Desolder the chip resistors on the switch PCB. The default resistance is 4.7k. You don't need fancy soldering iron or tweezers to do this, I did it with a safety lighter. Photo below
3. Replace the chip resistors with 100k 0805 chip resistors and reassemble. Then, install your modified switch back into your dash. You can get replacement resistors from Amazon.

Finished wiring under steering column:

 

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